STUDIES ON SEED TRANSMISSION OF Rhizoctonia solani IN FRENCH BEAN (Phaseolus vulgaris L.)
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Date
2018-06-21
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UHF,NAUNI
Abstract
ABSTRACT
The present investigation entitled “Studies on seed transmission of Rhizoctonia solani in French bean
(Phaseolus vulgaris L.)” was carried out in the Department of Seed Science and Technology, Dr. Y. S Parmar University of
Horticulture and Forestry, Nauni, Solan (HP) during 2016 to 2018. Three laboratory experiments were undertaken following
Completely Randomized Design. Under the first experiment Rhizoctonia solani infected plants of French bean cv.
Contender were categorized on the basis of the extent of plant infection and six treatment were kept viz., Leaves apparently
free from spots or very few minute spots less than 5 in number (T1), Spots covering <10% of the leaf area & pods having
1or 2 spots of less than 1cm diameter (T2), upto 20% of the leaf area & upto 5% of the pod area (T3), upto 30% of the leaf
area & upto 10% of the pod area (T4), upto 50% of the leaf area & upto 25% of the pod area (T5) and >50% of the leaf area
& 50% or more of pod area (T6). Seeds from the plants under different treatments were extracted separately and subjected to
seed quality and health testing following methods like Standard blotter paper methods, Roll paper method, Agar plate
method and Grow out test. Seed germination (%), vigour index Length & Mass and other seed quality parameters like
seedling establishment (%), speed of germination were found highest in T1 (leaves apparently free from spots or very few
minute spots less than 5 in number). Whereas the per cent infection of seed with R. solani, Fusarium sp. Alternaria sp.,
Aspergillus sp. and Trichothecium sp. was observed highest in T6 (Spots covering >50% of the leaf area & 50% or more of
pod area). In the second experiment harvested seeds of the same cultivar were categorised into 8 treatments viz., apparently
healthy seeds (T1), shrivelled seeds (T2), discoloured seeds (T3), discoloured+ shrivelled seeds (T4), apparently healthy seeds
surface sterilized with 1 % sodium hypochlorite (T5), shrivelled seeds surface sterilized with 1 % sodium hypochlorite (T6),
discoloured seeds surface sterilized with 1 % sodium hypochlorite (T7), discoloured+ shrivelled seeds surface sterilized with
1 % sodium hypochlorite (T8). The seeds were subjected to seed quality and health testing following the same methods as
under the first experiment. Seed germination (%), vigour index length & mass and other seed quality parameters like
seedling establishment (%), speed of germination were highest in apparently healthy seeds surface sterilized with 1 %
sodium hypochlorite (T5). Whereas the per cent infection of seed with R. solani, Fusarium sp. Alternaria sp., Aspergillus
sp. and Trichothecium sp. was highest in T4 (Discoloured+ Shrivelled seeds) followed by T3 (Discoloured seeds). In third
experiment, healthy seeds as well as infected seeds were treated with different fungicides like carbendazim, hexaconazole,
tebuconazole, difenoconazole, propiconazole, benomil each @ 2g/kg of seed and compared with un-treated control. The
seeds were subjected to seed quality and health testing following the same methods as under the first experiment. Seed
germination (%), vigour index Length & IMass and other seed quality parameters like seedling establishment (%), speed of
germination were highest in seed treated with carbendazim followed by benomil. From the present study it can be concluded
that in French bean cv. Contender infection of plants with Rhizoctonia solani caused reduction in seed quality and increase
in infection/contamination with this pathogen as well as other seed mycoflora like Fusarium sp., Alternaria sp., Aspergillus
sp. and Trichothecium sp. The deleterious effect of the plant infection on seed quality increased with increase in the level of
infection. The fungal pathogen R. solani was found both internally as well as externally seed borne in nature and the extent
of its seed transmission from plant to seed and from seed to seedling was recorded 39.72 and 37.46 per cent, respectively.
All the systemic fungicides tested as seed treatment reduced the seed infection with R. solani and other mycoflora. Some
fungicides like, tebuconazole, propiconazole, hexaconazole, however, showed some retarding effect on seedling growth and
establishment. Seed treatment with carbendazim or benomil @ 2g/ kg of seed was found effective in the management of
seed borne inoculum of R. in French bean.
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